Why so much data stored in C:/Users/*/My Documents?

[Tegus]

Music should not be saved in the documents folder. Which vendor did you use to buy the game?

You can change where the user data is stored by creating a file called userdir.txt beside the .exe file(for example, using steam, the folder would be C:\Program Files (x86)\Steam\steamapps\common\crusader kings ii)

Edit the file and write something like "C:\MyCK2Dir"(without the quotes), and you saves should now be saved in that folder instead

 

[Tegus]

You can delete the Documents/Paradox Interactive/Crusader Kings II whenever you want, it will be recreated at startup(restrictions in userdir.txt applies though).

Just don't forget to make a backup copy of savegames and/or screenshots first (they are now saved in the Documents/Paradox Interactive/Crusader Kings II folder)